Luxembourg needed just 11 working days to approve a probably illegal tax deal allowing Amazon.com to allocate a large part of its European Union profits to one of its companies that does not have to pay tax, the European Commission said.

"In the absence of a transfer pricing report, the Commission has doubts whether the Luxembourg tax authorities properly confirmed by the contested tax ruling that the transfer pricing arrangement presented in Amazon's ruling request reflected what a prudent independent operator acting under normal market conditions would have accepted," it said.

Next, the Commission will publish the document in the Official Journal of the European Union which will probably take a couple of weeks, after which interested parties have a month to submit their views to the Commission.

The Amazon probe is part of a wider crackdown on tax deals in Europe. Similar investigations were started into a deal Apple struck with the Irish government as well as into deals made by Fiat in Luxembourg and Starbucks in the Netherlands.

There are no deadlines to conclude these cases but the Commission wants to present first results by the second quarter of this year.